Technically, Bruce Variety is not in DC (it's in Bethesda) but it's one store that's definitely worth the drive across the line. It's a bit of a throwback to the old five and dime, the kind of place where you can find office and party supplies, notions and fabric cut by the yard, anything your 9 year old might need for a diorama, socks and underwear, tupperware and household cleaners, and the list goes on.
Some of my enthusiasm for Bruce Variety is nostalgic because it reminds me of Horton's, the general store of my childhood, lacking only the soda fountain and crabby women in blue smocks. These days, folks are more likely to shop at Target or Michael's or any number of other big box stores. Me, I prefer the more personal if somewhat more dusty merchandise and erratic inventory that Bruce Variety offers.